Roles of heteroatoms in electrocatalysts for alkaline water splitting: A review focusing on the reaction mechanism

Alkaline water splitting is a promising technology for "green hydrogen" generation. To improve its efficiency, highly robust catalysts are required to reduce the overpotential for low electrical power consumption. Heteroatom modification is one of the most effective strategies for boosting catalytic performance, as it can regulate the physicochemical properties of host catalysts to improve their intrinsic activity. Herein, aiming to provide an overview of the impact of heteroatoms on catalytic activity at the atomic level, we present a review of the key role of heteroatoms in enhancing reaction kinetics based on the reaction pathways of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. In particular, the introduction of heteroatoms can directly and indirectly optimize the interactions between the active sites and intermediates, thus improving the intrinsic activity. To clearly illustrate this influence in detail, we have summarized a series of representative heteroatom-modified electrocatalysts and discussed the important roles of heteroatoms in the OER and HER reaction pathways. Finally, some challenges and perspectives for heteroatom-modified electrodes are discussed. We hope that this review will be helpful for the development of efficient and low-cost electrocatalysts for water electrolysis and other energy conversion applications.